There may be no single cause of bipolar disorder (aka manic depression). Instead, research indicates the causes of bipolar disorder are probably a combination of biochemical, genetic and environmental factors that may trigger and perpetuate the chemical imbalances in the brain.
Net worth: $829 million. Telecommunications mogul Strive Masiyiwa is widely regarded as the richest man in Zimbabwe and is one of the richest men in Africa with a net worth of more than US$800 million.
Britain's richest sportsmen 2015. Rio Ferdinand and Sir Nick Faldo are among the slightly more surprising entries, as Jenson Button grabs a podium finish in the 2015 Sunday Times Rich List.